1. Field of the Invention
The present invention relates to a gradation image forming apparatus and a gradation image forming method for forming gradation images.
2. Description of the Related Art
A gradation image is often used in an image of a small number of colors (data amount) such as image material or a Web banner in addition to full-color computer graphics. The use of the gradation image enables formation of a picturesque and more natural image even when the number of colors is small.
For formation of such a gradation image, for example, Jpn. Pat. Appln. KOKAI Publication No. 9-259258 presents a method of generating gradation data which has a one-dimensional inclination based on a start color of a gradation image, a unit width for changing a grayscale therein, and a grayscale change rate for each unit width. According to the method of Publication No. 9-259258, gradation data can be generated from the start color of the gradation image, the inclination thereof, and a step width. Thus, it is not necessary to store all data of pixel values of the gradation image in memory, and the volume of data can be reduced.